The present invention relates to an installation and process for operating a generator absorption heat pump heating installation such as for example, space heating, water heating, etc. up to a calorific power of approximately 20 kW.
Known continuously operating absorption heat pump heating installations, normally with ammonia/water as the working substance solution, require a solution pump in order to pump the same from the absorber into the generator, optionally via a heat exchanger. Such solution pumps require motive energy, and need maintainance and are in part susceptible to faults.
In small capacity absorption cooling means such as disclosed in, for example, German Patent 842,352, an auxiliary gas is provided to avoid a solution pump; however, this proposal leads to a weak substance exchange and, consequently, requires not only a large apparatus, but considerably large heat exchange surfaces.
Absorption installations proposed in German Patent 427,278, can only be used in conjunction with the coolant water due to the necessary hydrostatic heights and the resulting overall height of the equipment and can consequently only be used for air conditioning purposes.
Absorption heating systems with direct heating of the generator by a generator absorbing high temperature energy make it possible to save primary energy in connection with the heating heat supply of buildings, because part of the necessary heat can be taken from the environment. However, the date two essential points have prevented the wide introduction of such heating installations and these points are interconnected. Firstly and as in heat pumps, the problem exists that the heating heat requirement of the building and the power availability of the heat pump behave in opposite ways with falling external temperatures, so that compared with refrigerating machines, which usually operate in a narrowly defined operating range, the question of partial load control is of particular significance for fuel saving. Secondly, only a very small primary energy saving can be expected on continuously operating absorption heat pumps, which are solely regulated via the ratio of the running time to the idle time, i.e. with conventional on-off controls because a large amount of the annual heating work has to be provided at temperatures above 0.degree. C., which leads to high idle time losses.
Therefore a large number of proposals have been made in, for example, DE-OS 31 49 005 and DE-OS 31 40 003, to so extend the conventional absorption heat pump that a single apparatus can provide both the maximum calorific power at the lowest outside temperature and the lower heat requirement in the partial load range.
However, according to these proposals, relatively complicated installations are required, which require considerable equipments and other components, such as heat exchangers, solenoid valves, connecting lines and controls, so that the additional plant costs for improving the annual heating figure cannot really be compensated. In addition, all known continuously operating absorption heat pump heating systems require a solution pump, which is a fault-prone unit consuming a not inconsiderable amount of operating current.
On the basis of a known proposal according to DE-OS 29 38 203, which can in particular be advantageously realized in conjunction with heat carrier circuits, as a multistage, periodically operating absorption heat pump for heat recovery and ventilation systems, the problem of the invention is to reduce the number of equipments and to make do as far as possible without fault-prone, maintainance-requiring and energy-consuming components or units.
In accordance with the present invention, a process for an operation of a generator absorption heat pump heating installation for space heating, water heating, etc. is provided in which heating energy to be supplied to the heating water to be heated flows back from the heating system and can be supplied by both high temperature heat taken from a directly heated generator and from a low temperature heat absorbed by an absorption heat pump. The absorption heat pump is operated with a periodic change of operating phases including generation with condensation and evaporation with absorption at difference pressure levels. In the generation phase high temperature heat is supplied through the generator to a working substance solution circuit and useful heat during the condensation of the resulting vapor of the condenser is supplied to the heating water. During the absorption phase the temperature heat is supplied to the coolant in an evaporator and as useful heat in the absorber is supplied to the heating water. Both the high and low temperature heat supply is ultimately switched on when the heating water return or supply temperature drops below a predetermined lower temperature limit and is switched off when the hot water return or supply temperature rises above a predetermined upper temperature.
A maximum or almost a maximum calorific power of the heat pump heating installation, in accordance with the present invention, is diverted at low external temperatures by a high temperature heat supply to the generator and from the generator to a working substance solution circuit of the absorption heat pump. The condensate produced in the condenser following the complete filling of the coolant accumulator is returned to the absorber in the absorption heat pump. The working substance solution is then used as a heat carrier between the generator and the condenser through which the heating liquid flows.
To obtain a very high heat absorption on the evaporator and performance figure rise on the generator and absorber operation of the heating installation, a predeterminable minimum running time is maintained.
In accordance with further features of the present invention, a monovalent alternative generator absorption heat pumping installation for space heating, water heating, etc. up to a calorific capacity of approximately 20 kW is provided with the heating installation including a heat pump means having the evaporator means heatable by external heat and through whose heat exchanger flows coolant. An absorber means connected on a cold vapor side to the evaporator includes a heat exchanger means through which heating liquid or water of the heating system flows. A condenser means is connected on a coolant side to the evaporator means and to the absorber means and includes a heat exchanger means through which heating liquid flows. A generator means directly heatable by primary energy includes a heat exchanger constructed as a thermosiphon connected to a working substance solution chamber of the absorber means at a low point and high point so as to permit natural working circulation and to the working substance accumulator means of the condenser means. Stop valve means are respectivley provided in coolant connecting lines between the evaporator and the absorber and between the condenser and the evaporator. The stop valve between the evaporator and the absorber includes a one-way valve for allowing a vapor flow only to the absorber, with the valve between the condenser and the evaporator including a one-way valve for only allowing a liquid flow to the evaporator and for closing when the evaporator is complete filled with coolant so as to permit a flow back into the absorber by a liquid coolant line. The heating liquid can be passed through the heat exchanger of the condenser during high temperature heating supply and through the heat exchanger of the absorber during low temperature heat supply. A switch over of the heating liquid flow can alternately be automatically performed by a changeover valve when the heating liquid return or supply temperature drops below predetermined upper and lower preset temperature limits.
The generator according to the present invention may include a waste gas cooler connected downstream of the condenser on the heating liquid side, and the generator and the absorber may be separated from one another with the absorber being constructed as a working substance solution accumulator.
Advantageously, vapor chambers of the absorber and the generator are connected by a vapor pressure compensating line, with a high outlet means for a rich solution and low outlet means for a weak solution being arranged in such a manner that a natural concentration stratification during a discharge of a solution can be utilized with a minimum reabsorption.
The absorber in accordance with the present invention may be provided with means which, during absorption, returns to a lower part of the absorber sprayed on solution and brings about a forced circulation for preventing stratification of a concentration of a solution. Additionally, at least one of the condenser is provided with a coolant accumulator and the evaporator is constructed as a coolant accumulator.
Furthermore, means are provided for stopping or closing a working substance solution accumulator when the maximum permitted filling does not permit a vapor flow from the evaporator to the condenser so as to bring about an entry of coolant into the absorber through a connecting line between the condenser and the absorber. The closing or stopping means may include, for example, a one-way flow valve.
In installation of the present invention, the working substance solution includes several coolant components having lower boiling fractions which remain in the coolant accumulator as the low temperature heat drops.
Advantageously, in accordance with further features of the present invention, a heat exchanger means may be interposed between the absorber and the generator.
The invention makes it possible to provide the heating energy with minimum equipment and without a solution pump. The disadvantage of periodically operating absorption installations, which consists of large parts of the installation and working substance solutions consisting of solvents and coolants having to be intermittently heated and cooled, through generation and absorption on the one hand, as well as evaporation and condensation on the other being carried out in separate equipments, so that the larger part of the overall installation remains constantly in the range of the useful temperature level and consequently the heat losses can be kept low through installation. The equipment volume and heat exchange surfaces are comparatively small, operation taking place at widely varying pressure levels through a periodic change of operating phase generation and absorption. Unlike the case of continuously operating absorption heat pumps, the operating phases of generation with condensation and evaporation with absorption take place in a time-separated manner.
The high temperature heat produced in the generator produces hot vapor, which is condensed in the condenser by the heating water and consequently supplies its useful heat, e.g. at 50.degree. C. to the heating water. The low temperature heat supplied at a different time to the evaporator leads to the production of cold vapor, which is condensed in the absorber and also at approximately 50.degree. C. gives off its useful heat to the heating water which is now passed through the absorber, after previously reversing the changeover valve.
Compared with periodically operating absorption refrigerating machines, which only provide refrigerating capacity during the evaporation phase, the heating installation according to the invention is usefully employed throughout the entire operating period, because either useful heat is supplied as condensation heat in the condenser or useful heat is supplied to the heating water to be heated in the absorber as absorption heat.
Due to the time separation between generation and absorption, it is possible to achieve an adequate substance exchange without the otherwise necessary solution pump, because the pressure level in the complete installation is raised or lowered (motionless apparatus). The decisive advantage of such a heating installation is consequently that the periodically operating absorption heat pump can be operated without any auxiliary energy, so that it functions in a substantially noiseless and maintainance-free manner.
The condenser, a container below the condenser or the evaporator can be constructed as coolant or refrigerant accumulators, so that all partial load operating points are then made possible with sliding working temperatures with optimum coupling in of heat from the ambient or environment (low temperature heat). As a function of the necessary heating water temperatures the calorific power of the installation is slidingly adapted to the heat requirements via the ratio of generator (burner) operating time to evaporator (absorber) operating time, it being appropriate to adhere to specific minimum running times. This means that slightly below the heating limit (e.g. 15.degree. C.), the maximum degassing scope of the working substance system used is fully utilized, whereas at the lowest design point (e.g. -10.degree. C.) the installation can pass into purely permanent generator operation (boiler operation), in which the working substance solution merely serves as a heat carrier.